Fuel injection system

ABSTRACT

A fuel injection system for internal combustion engines having a fuel injector that injects fuel into a combustion chamber, which is delimited by a cylinder wall in which a piston is guided, and having a spark plug that projects into the combustion chamber, the fuel injector injecting a plurality of injection jets into the combustion chamber. The injection jets generate a cone-shaped mixture cloud having an elliptical cross-section in the combustion chamber.

BACKGROUND INFORMATION

In mixture-compressing internal combustion engines having externalignition and internal mixture formation, stratified charge operationrequires a “mixture cloud” in the region of the spark plug, which musthave a particular fuel-air ratio in the ignitable region. For thispurpose, fuel injectors are used which include nozzles that open to theinside or to the outside and generate a conical jet.

From German Patent Application No. 198 04 463, a fuel injection systemfor a mixture-compressing internal combustion engine having externalignition is known, which includes at least one fuel injector thatinjects fuel into a combustion chamber having a piston/cylinder design,and which is provided with a spark plug projecting into the combustionchamber. The nozzle body of the fuel injector is provided used with atleast one row of injection orifices distributed across the circumferenceof the nozzle body. By a selective injection of fuel via the injectionorifices, a jet-controlled combustion method is realized by theformation of a mixture cloud, at least one jet being aimed in thedirection of the spark plug or its immediate vicinity. Additional jetsensure that an at least approximately continuous or cohesive mixturecloud is formed.

Disadvantageous in the fuel injector known from German PatentApplication No. 198 04 463 is, in particular, the incomplete utilizationof the available combustion chamber, which results in a low-qualitymixture formation due to an air proportion that is too high, andsubsequent superelevated emissions of unburned hydrocarbons caused byindividual combustion misses, as well as higher fuel consumption.

SUMMARY OF THE INVENTION

The fuel injector system according to the present invention has theadvantage over the related art that, as a result of the differentexpansion, in a longitudinal and a transverse direction of the internalcombustion engine, of the mixture cloud injected into the combustionchamber, and as a result of the elliptical cross-sectional form of themixture cloud resulting therefrom, the mixture cloud is able to be moreoptimally adapted to the shape of the combustion chamber, therebyallowing more effective combustion, lower fuel consumption and reducedpollutant emission.

It is particularly advantageous that the thermal shock load and thecarbon-fouling of the spark plug are able to be reduced by thetangential injection of fuel relative to the spark-plug position, sincethe injection jets are not aimed directly at the spark plug.

By a selective configuration of the spray-discharge orifices and, thus,the injection jets in the combustion chamber, the installation positionof the intake and discharge valves as well as the spark plug in thecylinder head may be advantageously taken into account, even though thecombustion-chamber geometry is still able to be optimally utilized.

The fuel injectors suited for the fuel injection system may beadvantageously produced in a cost-effective manner, without additionalproduction effort.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic section through an exemplary embodiment of aninternal combustion engine having a fuel injection system configuredaccording to the present invention.

FIGS. 2A and 2B show a schematic section, in a longitudinal directionand in a transverse direction, through the internal combustion engineand the fuel injection system according to the present invention.

FIG. 3 shows a schematic section through a mixture cloud generated in acombustion chamber of the internal combustion engine.

DETAILED DESCRIPTION

In a part-sectional view, FIG. 1 shows an exemplary embodiment of aninternal combustion engine 1 having a fuel injection system 2 accordingto the present invention.

Fuel injection system 2 includes a cylinder block having a cylinder wall13, in which a piston 6 is guided. A connecting rod 14 guides piston 6in its up-and-down movement along cylinder wall 13. A cylinder head 3seals off cylinder wall 13 at its extremity. Cylinder wall 13, piston 6and cylinder head 3 enclose a combustion chamber 7.

A fuel injector 5 is positioned in cylinder head 3, preferably in itscenter. A spark plug 4 is inserted in a bore of cylinder head 3 at aslight lateral offset. Moreover, at least one intake valve 11 and atleast one discharge valve 12 are present.

When fuel injection system 2 is in operation, injection jets (sprays)10, which together form a cone-shaped fuel jet, are injected intocombustion chamber 7 through spray-discharge openings present in fuelinjector 5. A mixture cloud 9 is formed by mixing fuel and air incombustion chamber 7. Mixture cloud 9 is ignited by spark plug 8. Theshape of the cone-shaped fuel jet according to the present invention isexplained in greater detail with the aid of FIGS. 2 and 3.

It can be inferred from FIG. 1 that combustion chamber 7 of internalcombustion engine 1 is designed in the form of a roof-shaped combustionchamber 7 in cylinder head 3, which includes ridge slopes 15 and a ridge16. Fuel injector 5 is located at ridge 16, whereas gas-exchange valves11 and 12 are located in ridge slopes 15. This is particularlyadvantageous when more than two gas exchange valves 11, 12 are used,since internal combustion engine 1 is more optimally supplied with airin this manner when operated at full load.

In order to be able to utilize combustion chamber 7 in an optimal mannerand take the position of intake and discharge valves 11, 12 intoaccount, the present invention provides for fuel injector 5 to bedesigned in such a way that injection jets 10, injected into combustionchamber 7 by fuel injector 5, are injected at an angle that is greaterin a longitudinal direction of internal combustion engine 1 than in atransverse direction of internal combustion engine 1.

To illustrate this measure, FIG. 2A shows a heavily schematizedlongitudinal section through an exemplary internal combustion engine 1having four cylinders, while FIG. 2B shows a section through one of thecylinders in a transverse direction of internal combustion engine 1.

As can be inferred from FIG. 2A, injection jets 10 are injected with theaid of fuel injector 5 under a maximum opening angle α, which isdetermined by the position of the spray-discharge orifices of fuelinjector 5.

In a transverse direction of internal combustion engine 1, injectionjets 10, as shown in FIG. 2B, are injected in accordance with ridgeslopes 15, which delimit combustion chamber 7, at an angle β, which issmaller than angle α. Gas-exchange valves 11 and 12 and also spark plug4 (not shown in FIG. 2B), thus, are only tangentially grazed byinjection jets 10 and are not directly exposed to injection jet 10. Thisis advantageous in particular in the case of spark plug 4, since thethermal shock load and deposit formation on the electrodes are reducedin this manner and the service life of spark plug 4 is extended.

A view of a section through injected mixture cloud 9 shows theelliptical form, which is due to the sizes of opening angles α and βdiffering from each other in two orthogonal spatial directions. Becauseof the lateral flattening of mixture cloud 9, it is optimally adapted tothe shape of combustion chamber 7.

The jet angles that are between the maximum opening angle α and theminimum opening angle β may then be continually approximated to theextreme values by using an arbitrary number of individual injection jets10. FIG. 3 shows, by way of example, a mixture cloud 9 made up of tenindividual injection jets 10. Maximum opening angle α is not assumed,but merely approximated by two adjacently located injection jets 10.Such a configuration may be advantageous, for instance, when two sparkplugs 4 are provided, which should not be exposed to a direct injectionso as to avoid the stress of thermal shock, spark plugs 4 being disposedin the sides of the roof ridge.

If spark plug 4 is located in the “roof ridge”, for example, minimumopening angle β is not assumed, but likewise approximated by twoadjacently located injection jets.

By using any desired number of spray-discharge orifices of fuel injector5, virtually any configuration of injection jets 10 may be generated.Jet clearance angle Y of individual injection jets 10 may be identicalor differ with respect to one another. The configuration of jetclearance angles Y is independent of the configuration of opening anglesα and β of mixture cloud 9.

The present invention is not restricted to the exemplary embodimentshown and, for instance, is also applicable to fuel injection systems 2that have more or fewer injection jets 10, gas-exchange valves 11, 12and, in particular, a plurality of spark plugs 4 as well as variabledisplacement volumes.

1. A fuel injection system system for an internal combustion engine, theengine including a combustion chamber which is delimited by a cylinderwall in which a piston is guided, the fuel injection system comprising:a spark plug that projects into the combustion chamber; and at least onefuel injector that injects fuel into the combustion chamber, the fuelinjector injecting a plurality of injection jets into the combustionchamber, the injection jets generating a cone-shaped mixture cloud inthe combustion chamber, the mixture cloud having an elliptical crosssection; wherein the mixture cloud has a first opening angle in alongitudinal direction of the engine, the mixture cloud having a secondopening angle in a transverse direction of the engine, the first openingangle being greater than the second opening angle.
 2. The fuel injectionsystem according to claim 1, wherein injection jets lying betweeninjection jets that are injected at the first and second opening angles,continuously approach the first and second opening angles.
 3. The fuelinjection system according to claim 1, wherein the second opening angleis a minimum opening angle aligned along ridge slopes.
 4. The fuelinjection system according to claim 1, wherein the fuel injector issituated at a ridge, delimited by ridge slopes, of a cylinder head. 5.The fuel injection system according to claim 1, wherein jet clearanceangles between individual ones of the injection jets are of equal size.6. The fuel injection system according to claim 1, wherein jet clearanceangles between individual ones of the injection jets are of differentsizes.
 7. The fuel injection system according to claim 1, wherein theinjection jets are aligned in such a way that they are tangentiallyaligned to the spark plug and gas-exchange valves situated in a cylinderhead of the engine.